HttpWebRequest.EndGetResponse(IAsyncResult) Metoda

Definice

Obor názvů:

System.Net

Sestavení:

System.Net.Requests.dll

Zdroj:

HttpWebRequest.cs

Ukončí asynchronní požadavek na internetový prostředek.

public:
 override System::Net::WebResponse ^ EndGetResponse(IAsyncResult ^ asyncResult);

public override System.Net.WebResponse EndGetResponse (IAsyncResult asyncResult);

override this.EndGetResponse : IAsyncResult -> System.Net.WebResponse

Public Overrides Function EndGetResponse (asyncResult As IAsyncResult) As WebResponse

Parametry

asyncResult

IAsyncResult

Čekající požadavek na odpověď.

Návraty

WebResponse

WebResponse obsahující odpověď z internetového prostředku.

Výjimky

ArgumentNullException

asyncResult je null.

InvalidOperationException

Tato metoda byla volána dříve pomocí asyncResult.

-nebo-

Vlastnost ContentLength je větší než 0, ale data nebyla zapsána do datového proudu požadavku.

WebException

Abort() byl dříve volána.

-nebo-

Při zpracování požadavku došlo k chybě.

ArgumentException

asyncResult nebyla vrácena aktuální instancí z volání BeginGetResponse(AsyncCallback, Object).

Příklady

Následující příklad kódu používá metodu EndGetResponse k ukončení asynchronního požadavku na internetový prostředek.

   static void RespCallback( IAsyncResult^ asynchronousResult )
   {
      try
      {
         
         // State of request is asynchronous.
         RequestState^ myRequestState = dynamic_cast<RequestState^>(asynchronousResult->AsyncState);
         HttpWebRequest^ myHttpWebRequest2 = myRequestState->request;
         myRequestState->response = dynamic_cast<HttpWebResponse^>(myHttpWebRequest2->EndGetResponse( asynchronousResult ));
         
         // Read the response into a Stream object.
         Stream^ responseStream = myRequestState->response->GetResponseStream();
         myRequestState->streamResponse = responseStream;
         
         // Begin the Reading of the contents of the HTML page and print it to the console.
         IAsyncResult^ asynchronousInputRead = responseStream->BeginRead( myRequestState->BufferRead, 0, BUFFER_SIZE, gcnew AsyncCallback( ReadCallBack ), myRequestState );
      }
      catch ( WebException^ e ) 
      {
         Console::WriteLine( "\nException raised!" );
         Console::WriteLine( "\nMessage: {0}", e->Message );
         Console::WriteLine( "\nStatus: {0}", e->Status );
      }

   }

   static void ReadCallBack( IAsyncResult^ asyncResult )
   {
      try
      {
         RequestState^ myRequestState = dynamic_cast<RequestState^>(asyncResult->AsyncState);
         Stream^ responseStream = myRequestState->streamResponse;
         int read = responseStream->EndRead( asyncResult );
         
         // Read the HTML page and then print it to the console.
         if ( read > 0 )
         {
            myRequestState->requestData->Append( Encoding::ASCII->GetString( myRequestState->BufferRead, 0, read ) );
            IAsyncResult^ asynchronousResult = responseStream->BeginRead( myRequestState->BufferRead, 0, BUFFER_SIZE, gcnew AsyncCallback( ReadCallBack ), myRequestState );
         }
         else
         {
            Console::WriteLine( "\nThe contents of the Html page are : " );
            if ( myRequestState->requestData->Length > 1 )
            {
               String^ stringContent;
               stringContent = myRequestState->requestData->ToString();
               Console::WriteLine( stringContent );
            }
            Console::WriteLine( "Press any key to continue.........." );
            Console::ReadLine();
            responseStream->Close();
            allDone->Set();
         }
      }
      catch ( WebException^ e ) 
      {
         Console::WriteLine( "\nException raised!" );
         Console::WriteLine( "\nMessage: {0}", e->Message );
         Console::WriteLine( "\nStatus: {0}", e->Status );
      }

   }

};

int main()
{
   try
   {
      
      // Create a HttpWebrequest object to the desired URL.
      HttpWebRequest^ myHttpWebRequest1 = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "http://www.contoso.com" ));
      
      // Create an instance of the RequestState and assign the previous myHttpWebRequest1
      // object to its request field.
      RequestState^ myRequestState = gcnew RequestState;
      myRequestState->request = myHttpWebRequest1;
      
      // Start the asynchronous request.
      IAsyncResult^ result = dynamic_cast<IAsyncResult^>(myHttpWebRequest1->BeginGetResponse( gcnew AsyncCallback( HttpWebRequest_BeginGetResponse::RespCallback ), myRequestState ));
      HttpWebRequest_BeginGetResponse::allDone->WaitOne();
      
      // Release the HttpWebResponse resource.
      myRequestState->response->Close();
   }
   catch ( WebException^ e ) 
   {
      Console::WriteLine( "\nException raised!" );
      Console::WriteLine( "\nMessage: {0}", e->Message );
      Console::WriteLine( "\nStatus: {0}", e->Status );
      Console::WriteLine( "Press any key to continue.........." );
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "\nException raised!" );
      Console::WriteLine( "Source : {0} ", e->Source );
      Console::WriteLine( "Message : {0} ", e->Message );
      Console::WriteLine( "Press any key to continue.........." );
      Console::Read();
   }

}

  try
  {

    // Create a HttpWebrequest object to the desired URL.
    HttpWebRequest myHttpWebRequest1= (HttpWebRequest)WebRequest.Create("http://www.contoso.com");

    // Create an instance of the RequestState and assign the previous myHttpWebRequest1
    // object to it's request field.
    RequestState myRequestState = new RequestState();
    myRequestState.request = myHttpWebRequest1;

    // Start the asynchronous request.
    IAsyncResult result=
      (IAsyncResult) myHttpWebRequest1.BeginGetResponse(new AsyncCallback(RespCallback),myRequestState);

    allDone.WaitOne();

    // Release the HttpWebResponse resource.
    myRequestState.response.Close();
  }
  catch(WebException e)
  {
    Console.WriteLine("\nException raised!");
    Console.WriteLine("\nMessage:{0}",e.Message);
    Console.WriteLine("\nStatus:{0}",e.Status);
    Console.WriteLine("Press any key to continue..........");
  }
  catch(Exception e)
  {
    Console.WriteLine("\nException raised!");
    Console.WriteLine("Source :{0} " , e.Source);
    Console.WriteLine("Message :{0} " , e.Message);
    Console.WriteLine("Press any key to continue..........");
    Console.Read();
  }
}
private static void RespCallback(IAsyncResult asynchronousResult)
{
  try
  {
    // State of request is asynchronous.
    RequestState myRequestState=(RequestState) asynchronousResult.AsyncState;
    HttpWebRequest  myHttpWebRequest2=myRequestState.request;
    myRequestState.response = (HttpWebResponse) myHttpWebRequest2.EndGetResponse(asynchronousResult);

    // Read the response into a Stream object.
    Stream responseStream = myRequestState.response.GetResponseStream();
    myRequestState.streamResponse=responseStream;

    // Begin the Reading of the contents of the HTML page and print it to the console.
    IAsyncResult asynchronousInputRead = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
  }
  catch(WebException e)
  {
    Console.WriteLine("\nException raised!");
    Console.WriteLine("\nMessage:{0}",e.Message);
    Console.WriteLine("\nStatus:{0}",e.Status);
  }
}
private static  void ReadCallBack(IAsyncResult asyncResult)
{
  try
  {

  RequestState myRequestState = (RequestState)asyncResult.AsyncState;
  Stream responseStream = myRequestState.streamResponse;
  int read = responseStream.EndRead( asyncResult );
  // Read the HTML page and then print it to the console.
  if (read > 0)
  {
    myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.BufferRead, 0, read));
    IAsyncResult asynchronousResult = responseStream.BeginRead( myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
  }
  else
  {
    Console.WriteLine("\nThe contents of the Html page are : ");
    if(myRequestState.requestData.Length>1)
    {
      string stringContent;
      stringContent = myRequestState.requestData.ToString();
      Console.WriteLine(stringContent);
    }
    Console.WriteLine("Press any key to continue..........");
    Console.ReadLine();

    responseStream.Close();
    allDone.Set();
  }
  }
  catch(WebException e)
  {
    Console.WriteLine("\nException raised!");
    Console.WriteLine("\nMessage:{0}",e.Message);
    Console.WriteLine("\nStatus:{0}",e.Status);
  }
}

  Try
    ' Create a new HttpWebrequest object to the desired URL.
    Dim myHttpWebRequest1 As HttpWebRequest = CType(WebRequest.Create("http://www.contoso.com"), HttpWebRequest)
    
    ' Create an instance of the RequestState and assign the previous myHttpWebRequest1
    ' object to it's request field.  
    Dim myRequestState As New RequestState()
    myRequestState.request = myHttpWebRequest1
    
    ' Start the Asynchronous request.
    Dim result As IAsyncResult = CType(myHttpWebRequest1.BeginGetResponse(AddressOf RespCallback, myRequestState), IAsyncResult)
    allDone.WaitOne()
  
    ' Release the HttpWebResponse resource.
    myRequestState.response.Close()
  Catch e As WebException
    Console.WriteLine(ControlChars.Cr + "Exception raised!")
    Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
    Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
    Console.WriteLine("Press any key to continue..........")
  
  Catch e As Exception
    Console.WriteLine(ControlChars.Cr + "Exception raised!")
    Console.WriteLine("Source :{0} ", e.Source)
    Console.WriteLine("Message : {0}", e.Message)
    Console.WriteLine("Press any key to continue..........")
    Console.Read()
  End Try
End Sub

Private Shared Sub RespCallback(asynchronousResult As IAsyncResult)
  Try
    ' State of request is asynchronous.
    Dim myRequestState As RequestState = CType(asynchronousResult.AsyncState, RequestState)
    Dim myHttpWebRequest2 As HttpWebRequest = myRequestState.request
    myRequestState.response = CType(myHttpWebRequest2.EndGetResponse(asynchronousResult), HttpWebResponse)
    ' Read the response into a Stream object.
    Dim responseStream As Stream = myRequestState.response.GetResponseStream()
    myRequestState.streamResponse = responseStream
    ' Begin the Reading of the contents of the HTML page and print it to the console.
    Dim asynchronousInputRead As IAsyncResult = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, AddressOf ReadCallBack, myRequestState)
  Catch e As WebException
    Console.WriteLine(ControlChars.Cr + "Exception raised!")
    Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
    Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
  End Try 
End Sub

Private Shared Sub ReadCallBack(asyncResult As IAsyncResult)
  Try
    Dim myRequestState As RequestState = CType(asyncResult.AsyncState, RequestState)
    Dim responseStream As Stream = myRequestState.streamResponse
    Dim read As Integer = responseStream.EndRead(asyncResult)
    '  Read the HTML page and then print it to the console.
    If read > 0 Then
      myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.BufferRead, 0, read))
      Dim asynchronousResult As IAsyncResult = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, AddressOf ReadCallBack, myRequestState)
    Else
      Console.WriteLine(ControlChars.Cr + "The contents of the Html page are : ")
      If myRequestState.requestData.Length > 1 Then
        Dim stringContent As String
        stringContent = myRequestState.requestData.ToString()
        Console.WriteLine(stringContent)
      End If
      Console.WriteLine("Press any key to continue..........")
      Console.ReadLine()
      responseStream.Close()
      allDone.Set()
    End If
  Catch e As WebException
    Console.WriteLine(ControlChars.Cr + "Exception raised!")
    Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
    Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
  End Try 
End Sub

Poznámky

Opatrnost

WebRequest, HttpWebRequest, ServicePointa WebClient jsou zastaralé a neměli byste je používat pro nový vývoj. Místo toho použijte HttpClient.

Metoda EndGetResponse dokončí asynchronní požadavek na internetový prostředek, který byl spuštěn voláním metody BeginGetResponse.

Opatrnost

Pokud chcete datový proud zavřít a uvolnit připojení, musíte volat metodu Close. Pokud to neuděláte, může dojít k tomu, že aplikace dojde k výpadku připojení.

Poznámka

Tento člen vypíše informace o trasování, když ve své aplikaci povolíte trasování sítě. Další informace naleznete v tématu Trasování sítě v rozhraní .NET Framework.